Radiation responsive device



y 3, 1956 c. I. MARTKNEZ 2,753,418

RADIATION RESPONSIVE DEVICE Filed May 6. 1953 a I [1% RAD/ANT HEAT 1+ oi i {/V-3 +1 TIME mp (sEcoA/ps) -vv m a NORMAL RAD/A TION [NI-EA D BAD/ANT FLUX INVENTOR CLE MEN TL MAEfl/VEZ United States Patent RADIATION RESPONSIVE DEVICE Clement I. Martinez, Rochelle Park, N. J., assignor to International Telephone and Telegraph Corporation, a corporation of Maryland Application May 6, 195-3, Serial No. 353,331 9 Claims. (Cl. 200-137) This invention relates to thermally responsive devices and more particularly to a switch which is responsive to a change in the radiant energy of a given source while remaining insensitive to wide changes of temperature in the surrounding atmosphere.

In the copending application of L. Rosenberg and R. Lewthwaite, Serial No. 343,154, filed March 18, 1953, a radiant heat detector is disclosed employing two members of the same material, or of a material substantially of the same coefiicient expansion, in which one is sturdier than the second and Where the second is disposed to present a larger proportion of its area toward a source of radiant energy than the sturdier member. This insures that the second member will absorb more heat and will expand more quickly than the sturdier member upon a sudden change in the radiant heat. This results in a differential of expansion causing the less sturdier one to move or bow relative to the other, such relative movement being employed to actuate an associated switch. An object of the present invention is to provide asirnilar heat radiation responsive device of simple, rugged construction and relatively easy to manufacture.

A further object is to provide a radiant heat responsive switch having an inverse time-overload operating characteristic and in which the tripping point is adjustable.

One of the main features of the invention is the simplicity of construction and its sensitivity to small changes in the radiant temperature of a given source of heat. The sturdier member is preferably made of channel material having an elongated opening therethrough. The second member, which is preferably of strip material, is anchored .at: its ends to the channel member for exposure through the opening contained in the channel member. An adjustable switch support is mounted within the channel member and provided with adjutsable means for varying the position of the switch carried. thereby with respect to the strip member. The support also includes a resilient backing element which has one portion adapted to resiliently engage the mid portion of the strip crosswise thereof and another portion to engage and thereby transfer any tripping movement of this strip to the actuating element of the switch. By positioning the device so that the exposed area of the strip member is directed toward the source of heat, small changes in radiant energy will cause the strip to expand more rapidly than the channel member thereby causing it to bow laterally, thereby causing movement of the resilient member for actuation of the switch.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a longitudinal cross-sectional View of the radiation responsive device of this invention, the sectional view being taken along line 11 of Fig. 2;

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Fig. 2 is a plan view taken along line 2-2 of Fig. 1 showing the back side of the device;

Fig. 3 is a cross-sectional view taken along line 3-3 of Fig. 1; and

Fig. 4 is a graphical representation illustrating the tripping characteristics of the device.

Referring to the drawing, the radiation responsive device is shown to comprise a channel member 1 and a flexible strip member 2. As shown more clearly in Fig. 3, the channel member 1 comprises a center wall portion 3 and two side wall portions 4 and 5. The center wall portion 3 is provided with an elongated rectangular opening 6. The strip 2 underlies the opening 6 and is anchored at the ends thereof to the center wall portion as indicated by spot welding 7 and 8. While the two members are secured together by welding, other means of fastening two members may, of course, be employed. The opening 6 is wider than the strip 2 whereby the strip may be bowed outwardly therethrough without contacting the side edges of the opening.

A switch supporting member 10 of rigid strip form. is provided having at one end thereof flanges 11 and 12 which may be fastened to the side flanges 4 and 5 as indicated by the screw elements 13 and 14. The strip 10 extends lengthwise of the channel member and is adjustably supported on a threaded pin 15 carried by the center Surrounding the pin is 10 outwardly while the. end of the pin carries a nut 17 to determine the desired. position of the support. Carried by the supporting strip the snap-acting type eom-- wall 3 of the channel member. a spring 16 to urge the support 10 is a switch 18 preferably of monly known as the Micro-switch. The snap-acting type of switch is preferred in this device over the use of contacts carried by members 1 and 2 because of the tendency of such contacts to arc. Also carried by the supporting strip 10 is a resilient backing element 19 supported at one end as indicated at 20 and extending Withthe other end portion in resilient engagement with and crosswise of the mid portion 9 of the flexible strip 2. The switch 18 is located so that the actuating element 21 thereof may be engaged by the resilient element 19 at a point slightly removed from the extreme end of the element 19. The resilient element 19 provides a resilient backing force for the stripand is of nearly the same width so asto transfer in a sensitive manner any expansion or contraction movement of the strip 2. The supporting strip 10 is provided with a lengthwise flange 22 to stiffen it' and for sliding engagement with the side wall 4 of the channel member. The end portion of the supporting strip 10 adjacent itsfixed mounting is provided with a small cutout 23 to insure hinge action adjacent its fixed support.

The. exposed face of the sensitive member 2 is preferably blackened to enhance its absorption of radiant heat while the surfaces of member 1 are white or shiny to reduce absorptionof radiant heat. The unit as a whole is adapted for mounting adjacent a given source of radiant heat, such as-a radiation cooled type of vacuum tube or other instrument, the overheating of which is to be checked. The opening 6' is such as to expose nearly all of the sensitive. flexible member 2, the total exposed area thereof being a greater proportion of its overall area as compared to the face portions of the central wall 3 of the channel member 1. This difference in the relative proportion of exposed area as well as the difference in thermal capacity or mass of the two members insures a quick response in changes to radiant energy. By adjusting the nut 17 the device may be set to receive a normal amount of radiant energy without actuation of the switch 18. However, should the source of radiant energy increase in temperature beyond that for which the device is adjusted it will cause the sensitive strip 2 to expand more rapidly than the channel member 1,

thereby moving laterally to cause actuation of switch 18. For example, it will remain non-actuated for long periods of time while exposed to a radio tube dissipating its rated power and yet be actuated when this power makes a sudden rise. The radiation responsive device maintains this performance without adjustment under wide changes in surrounding air temperature, satisfactory consistent tests having been made between 20 and +80 C.

In Fig. 4 the tripping characteristics of the radiation responsive device is shown as having an inverse timeoverload tripping characteristic. Radiant flux line 24 represents the normal radiation of a given heat source such as a vacuum tube of the radiation cooled type wherein the anode is normally maintained at a high temperature. In tests made this line represented the 100% normal ioad to which the device was adjusted. In one of the examples for which the curve of Fig. 4 is given, the face of the device was placed a distance of 2% inches from the anode surface of a 4-400 Eimac tube. The curve 25 is shown to have breadth because of some slight variations found in different models tested. In other words, the width of the curve represents a certain latitude of operation. in practice, the device is adjusted under normal radiation until the switch is activated whereupon its adjustment is backed off slightly. As shown by the curve 25 slight changes of radiation beyond normal will operate the device, the greater the change the more promptly the actuation. The switch 18 may be connected either in an alarm circuit or in the control circuit of the tube or other apparatus being observed.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

I claim:

1. A radiant responsive device comprising first and second members of substantially the same coeflicient of expansion, means anchoring said second member to said first member at points spaced apart with the mid-portion of said second member free to move laterally with respect to said first member upon the occurrence of a differential expansion of said members, a switch having an actuator element, means supporting said switch from said first member and a resilient transfer element disposed with one portion thereof adjacent the mid-portion of said second member and another portion thereof adjacent said actuating element for transfer of movement from said second member to said actuating element.

2. A radiant responsive device according to claim 1, wherein the means supporting said switch is provided with means for adjusting the position of said switch relative to the mid-portion of said second member.

3. A radiant responsive device according to claim 1,

wherein said resilient transfer element has one end anchored to said first member with the other end thereof in resilient engagement with the mid-portion of said second member.

' 4. A radiant responsive device according to claim 1, wherein said first member has a wall with an opening extending therethrough and said second member comprises a flat strip exposed through said opening.

5. A radiant responsive device comprising a relatively sturdy member having an elongated opening therethrough, a relatively flexible member anchored at its ends to said sturdy member with the mid-portion of said flexible member exposed through said opening, a switch, and means carried by said sturdy member supporting said switch for actuation by movement of said flexible member relative to said sturdy member, said sturdy member being channel shaped having a center wall and two side Walls and said opening is located in said center wall, and said flexible member comprises a flat strip disposed lengthwise of said opening with the ends thereof connected to said center wall at opposite ends of said opening.

6. A radiant responsive device according to claim 5, further including a resilient transfer element carried by said channel shaped member with one end portion, extending adjacent said switch and in resilient engagement with the backside of said flexible member, said switch having an actuating element adapted to be engaged by said transfer element upon relative movement of said flexible member with respect to said channel member.

7. A radiant responsive device according to claim 5, wherein the means supporting said switch includes a relatively rigid member hinged at one end to said channel member and having means'at the other end thereof for adjusting that portion relative to the center wall of said channel member.

8. A radiant responsive device comprising a channel member having a center wall and two side walls, said center wall having an elongated opening therethrough, a flexible strip of material of substantially the same coefiicient of expansion as said channel member, said flexible strip being anchored at the ends thereof to said center wall at opposite ends of said elongated opening, said strip being normally bowed so that the major portion thereof extends into said opening, said flexible strip being narrower than the width of said opening, a switch having an actuating element, a relatively rigid member anchored at one end to said channel member to support said switch adjacent the mid-portion of said flexible strip, and means associated with the free end of said rigid support member to adjust its position relative to said center wall to thereby determine the location of the actuating element of said switch with respect to the mid-portion of said flexible strip.

9. A radiant responsive device according to claim 8, further including a resilient backing strip having one end thereof anchored to said channel member and the other end disposed between said actuating element and the midportion of said flexible strip for engagement therewith to effect transfer of movement from said flexible strip to said actuating element.

References Cited in the file of this patent UNITED STATES PATENTS 2,211,700 Maynard Aug. 13, 1940 2,299,533 Cyr Oct. 20, 1942 2,389,686 Reingruber et al Nov. 27, 1945 2,602,128 Reingruber et al. July 1,- 1952 I FOREIGN PATENTS 6,777 Great Britain Sept. 17, 1914 

